Leptophilic Dark Matter from the Lepton Asymmetry
Timothy Cohen, Kathryn M. Zurek
TL;DR
A model of weak scale dark matter where the thermal DM density is set by the lepton asymmetry due to the presence of higher dimension lepton violating operators is presented, giving a natural explanation for the observed cosmic ray electron and positron excesses, without resorting to a Sommerfeld enhancement.
Abstract
We present a model of weak scale Dark Matter (DM) where the thermal DM density is set by the lepton asymmetry due to the presence of higher dimension lepton violating operators. In these models there is generically a separation between the annihilation cross-section responsible for the relic abundance (through lepton violating operators) and the annihilation cross-section that is relevant for the indirect detection of DM (through lepton preserving operators). Due to this separation, there is a perceived boost in the annihilation cross-section in the galaxy today relative to that derived for canonical thermal freeze-out. This results in a natural explanation for the observed cosmic ray electron and positron excesses, without resorting to a Sommerfeld enhancement. Generating the indirect signals also sets the magnitude of the direct detection cross-section which implies a signal for the next generation of experiments. More generically these models motivate continued searches for DM with apparently non-thermal annihilation cross-sections. The DM may also play a role in radiatively generating Majorana neutrino masses.